Various modifications for testing of precurser-generated inflow

apps/gpu/LBM/BoundaryLayer/BoundaryLayer.cpp

src/gpu/GridGenerator/grid/BoundaryConditions/Side.cpp

src/gpu/VirtualFluids_GPU/GPU/GPU_Interface.h

src/gpu/VirtualFluids_GPU/GPU/GPU_Kernels.cuh

src/gpu/VirtualFluids_GPU/GPU/LBMKernel.cu

src/gpu/VirtualFluids_GPU/GPU/PrecursorBC.cu

src/gpu/VirtualFluids_GPU/KernelManager/BCKernelManager.cpp

...tualFluids_GPU/PreCollisionInteractor/Probes/PlaneProbe.h

...u/VirtualFluids_GPU/PreCollisionInteractor/Probes/Probe.h